It's all been said already, so just adding my "don't do it" OP.
A friend of mine bought a pony after riding at a riding school for about 8 years. Said friend thought she knew it all - it's an easy and common mistake to make, as until you've looked after a pony, you can have no concept of how much knowledge is required to meet the pony's basic needs, or how time consuming it is.
A year down the line, she regrets ever getting the pony, and this is someone who willingly paid in excess of £2500 for it, had spent a good 8 months researching it, and 8 years learning to ride prior to buying it.
It often comes as a big shock to people, just how little you know versus how much you need to know, how much you think it will cost versus how much it actually does cost, and how much time it will eat up, versus how much time it actually does take.
Yes, and you can't just give them to a riding school, or an animal shelter!
Definitely get a clause in the contract that funds won't be transferred unless the horses are removed from the field.